The invention is concerned with thermal cracking of hydrocarbons to produce olefins. It is particularly concerned with a catalytic method of enhancing the yield of olefins from the process.
Thermal cracking is a process wherein a hydrocarbon is converted to a new form by the influence of heat. The present invention is concerned with such a process used for olefin production.
The process is carried out in a cracking furnace that comprises a fire box enclosing a serpentine array of tubing. The array comprises a plurality of interconnected tubes and fittings totalling several hundred meters in length. The tubing array is maintained at a carefully controlled temperature, usually at least 750.degree. C., while the furnace is in operation.
The process involves passing a gaseous stream containing the feedstock through the heated tubing under pressure and at a high velocity. The resulting product is quenched as it exits the furnace, and is collected for further processing.
In converting hydrocarbons, it is customary to mix the hydrocarbons with steam as a diluent. The presence of steam enhances the yield, presumably because it prevents side reactions which partially consume the desired end product. It would be desirable to further enhance the yield, and it is a purpose of the present invention to provide such enhancement.
It has long been known that the presence of specific barium compounds serves to catalyze a wide variety of organic chemical reactions. In particular, a thermal cracking process has been described in which a hydrocarbon is mixed with hot combustion gases containing a finely divided metal oxide. A number of oxides are given as examples, barium oxide being one of the oxides listed.
For whatever reason, such catalytic efforts to enhance olefin output, except for the use of steam, have not found commercial favor. One need, of course, is to provide an inexpensive, convenient method of providing effective contact between the catalyst and the feedstock. Another need is to avoid contaminating the product and/or requiring an expensive means of separation. The present invention meets these needs.